Wall-mounted light switches which include a dimmer have become increasingly popular, especially for applications where it is desired to precisely control the level of light intensity in a particular room. Such dimmer switches usually employ a variable resistor which is manipulated by hand to control the switching of a triac which in turn varies the voltage input to the lamp to be dimmed.
This type of dimmer switch is simple and easy to construct, but offers limited flexibility. One feature this type of dimmer switch lacks is the ability to return to a preselected light intensity level after having been turned to full power. This type of dimmer switch has no memory to enable it to do this, however, and preselected light intensity levels established previously can be reestablished only by trial and error in manipulating the variable resistor.
There exist touch actuator controls which address some of the limitations of the manually-operated variable resistor dimmer switches just described. One such touch actuator control cycles repetitively through a range of intensities from dim to bright in response to extended touch inputs. A memory function is provided such that, when the touch input is removed, the cycle will be stopped and the level of light intensity at that point in the cycle will be stored in a memory. A subsequent short touch input will turn the light off, and a further short touch input will turn the light on at the intensity level stored in the memory. While this type of switch is an improvement over manually-operated variable resistor dimmer switches, it requires the user to go through the cycle of intensity levels in order to arrive at a desired intensity level. In addition, it still lacks the ability to return to a desired intensity level after having been set to full light output. A user must go through the cycle again until he or she finds the light intensity level desired. Moreover, this type of switch has no ability to perform certain aesthetic effects such as a gradual fade from one light intensity level to another.
U.S. Pat. No. 4,649,323 discloses a microcomputer-controlled light control which provides a fade function. The control disclosed in that patent is operated by a pair of non-latching switches which provide inputs to a microcomputer. The microcomputer is programmed to determine whether the switches are tapped or held (i.e., whether they are touched for a transitory duration or for a longer period of time). When a switch is held, the light intensity is either decreased or increased, and release of the switch causes the intensity setting to be entered into a memory. If the control is operating at a static light intensity level, a tap of a switch will cause the light intensity level to fade toward a predetermined level, either off, full on or a preset level. A tap while the light intensity level is fading will cause the fade to be terminated and cause the light intensity level to shift immediately and abruptly to either full on or full off, depending on which switch was tapped. This type of control, however, is not without drawbacks of its own. For example, a single tap by a user is interpreted in either of two very different ways (initiate fade or terminate fade), depending on the state of the control at the time the user applies the tap to a switch. This can be confusing to a user, who may erroneously terminate a fade when it is desired to initiate a fade, and vice versa. In addition, it is not possible to reverse a fade by a subsequent tap of the same switch while a fade is in progress. Instead, a tap while the control is fading in one direction will not reverse the direction of the fade but will cause the control to "jump" to either full on or full off. An abrupt shift from a low intensity level to full on, or from a high intensity to no light at all (full off) can be quite startling to the user and others in the area (and even dangerous, if the user and others are suddenly plunged into darkness).
The control disclosed in U.S. Pat. No. 4,649,323 also lacks a longduration fade to off, as do the other prior control designs. In many cases, it is desirable for a user to be able to have the lights fade out gradually. For example, a user may wish to turn out bedroom lights before retiring, but still have sufficient light to safely make his or her way from the control location to the bed before the lights are completely extinguished. There may also be situations where the night staff of a large building may need to extinguish ambient lights from a central location which is located some distance away from an exit, and may need a gradually decreasing level of illumination in order to walk safely to the exit. These situations would not be possible with the prior control, which would offer the user either almost immediate darkness or a constant level of intensity throughout the night, neither of which would be acceptable.
Also disclosed in the above-mentioned patent is a vertical array of indicator lights (e.g. light-emitting diodes or LED's) which indicate the present intensity level of the lighting load (lamp) controlled by the dimmer. Thus, if the lamp is operated at about 50% intensity, the LED in the middle of the array is energized, all other LED's being turned OFF. When the lamp is OFF, all LED's in the array are OFF, thereby indicating the ON/OFF state of the lamp. When the lamp is operating at full intensity, the top-most LED in the array is energized. While this type of status indicator affords certain advantages, it provides no indication to the user of the preset (i.e. stored) intensity level to which the lamp will become energized from an OFF state. While certain commercially available dimmer products solve this problem by always energizing (even when the lamp is-OFF) one LED in the array representing the stored preset level, such products are disadvantageous in that the preset level cannot be easily determined from the position of the energized LED in a totally darkened environment; that is, when only one LED is energized, its relative position in the array cannot be seen in the dark. A dimmer of this type is the MICRODIM (TM) lighting control, Model 10601-P, made by Leviton Manufacturing Co., Inc.
There is thus a need for an improved lighting control and dimming device which offers advantages not possible with prior controls while avoiding the drawbacks of the prior controls. The present invention fills that need.